fix: CI

[matiasbenary]

The CI keeps breaking, either because we run out of memory or because something happens with crowdin.

This PR makes three important changes:

1. It separates the logic of downloading translations and building from uploading them
2. It uses a cache to improve the time of building in the CI
3. Starts using a branch build to leave a built version of the docs

In this way, now we fully use Github CI to build or docs, instead of relying on Render to do so. Now Render only deals with hosting the already built website that our new CI outputs.

The new CI works in the following way:

• When somebody merges a PR, the action uploads the new content to crowdin, and then builds for all languages
• Manually we need to execute the translation pipeline, so it downloads the translations from crowdin and builds again into the docs.

Important: The translation pipeline also executes automatically once per week, so in case no PRs are made, but translations exists, they are taken into consideration.